Liquid Crystal Display Device

ABSTRACT

The present invention provides a liquid crystal display device having a linear light source, which is easily treated, in consideration of the heat radiation of a light-emitting diode in the liquid crystal display using the light-emitting diode as a light source. 
     A light-emitting diode  150  is provided on a metal substrate  161.  The metal substrate  161  is formed in a case shape such that the heat generated at the light-emitting diode  150  received in the case is efficiently radiated. A resin material  175  is filled in the metal case to form a plate-shaped light source  130.  It is possible to improve reliability during the handling in the manufacturing process by filling the resin material  175  to form the plate-shaped light source. It is possible to improve heat radiation effect by filling the resin material  157.

CLAIM OF PRIORITY

The present application claims priority from Japanese Application JP2006-107315 filed on Apr. 10, 2006, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light source of a non-self lightemission type display device, and more particularly to a liquid crystaldisplay device having a backlight using a light-emitting device as alight source.

2. Description of the Related Art

Recently, a liquid crystal display device is widely used as a displaydevice. In particular, the liquid crystal display device is of a thintype having a small thickness with light weight and low powerconsumption, and thus is used as a display unit of a mobile apparatus.

However, since the liquid crystal display is not of the self lightemission type, light irradiation means is required. In general, as thelight irradiation device used in the liquid crystal display device, aplanar light irradiation device called a backlight is widely used.Conventionally, a cold cathode discharge tube is used in alight-emitting device (also referred to as a light source) of abacklight. However, recently, a light-emitting diode (hereinafter,referred to as LED) is also used as the light-emitting device of amobile apparatus.

Japanese Laid-Open Patent Publication No. Sho. 64-88426 discloses aliquid crystal display device using a LED as a light source. JapaneseLaid-Open Patent Publication No. 2002-162626A describes a technologyrelating to heat radiation of an LED.

SUMMARY OF THE INVENTION

However, when a plurality of LEDs is used as a backlight to increasebrightness, an operation temperature increases and light emissionefficiency deteriorates. Accordingly, a metal plate and the like areused in consideration of heat radiation. Since it is difficult to form aheat radiation member on the light emission surface of the LED, thestructure is restricted in view of the heat radiation and lightemission. In addition, since the handling in the manufacturing processis difficult, the reliability of the structure is reduced.

Accordingly, the present invention is contrived to solve theabove-mentioned problems. An object of the invention is to provide aliquid crystal display device that includes a backlight and a lightsource with high reliability and that can be easily handled in themanufacturing process in view of the heat radiation of the backlight.

In order to accomplish the above-described object, according to anaspect of the invention, there is provided a liquid crystal displaydevice including: a liquid crystal display panel in which a liquidcrystal layer is provided between a pair of transparent substrateshaving electrodes for forming pixels therein; and a backlight whichirradiates light to the rear surface of the liquid crystal displaypenal, wherein the backlight has a plurality of light-emitting elements,a circuit substrate on which the plurality of light-emitting elementsare arranged, and a metal case for receiving the circuit substrate, andis integrally formed by filling a resin material on the circuitsubstrate in the metal case.

According to another aspect of the invention, there is provided a liquidcrystal display device including: a liquid crystal display panel inwhich a liquid crystal layer is provided between a pair of transparentsubstrates having electrodes for forming pixels therein; and a planarlight source which irradiates light to the rear surface of the liquidcrystal display penal, wherein the planar light source has a pluralityof light-emitting diodes arranged linearly, a circuit substrate forelectrically connecting the plurality of light-emitting diodes, and acase having side surfaces and a bottom surface for receiving the circuitsubstrate, and is integrally formed by filling a resin material betweenthe plurality of light-emitting diodes and the side surfaces in thecase.

According to another aspect of the invention, there is provided a liquidcrystal display device including: a liquid crystal display panel inwhich a liquid crystal layer is provided between a pair of transparentsubstrates having electrodes for forming pixels therein; a backlightwhich irradiates light to the rear surface of the liquid crystal displaypenal; and a control unit which controls the liquid crystal displaypanel, wherein the backlight has a light guiding plate and aplate-shaped light source formed along one side of the light guidingplate, the plate-shaped light source has a light-emitting surface, abottom facing the light-emitting surface, and side surfaces formed onthe circumference of the bottom; the bottom has a metal surface, aninsulating layer covering the metal surface, and an interconnectionprovided on the insulating layer; the plurality of light-emitting diodesare electrically connected to the interconnection; an opening are formedin the side surfaces or the bottom; a connection wiring for electricallyconnecting the plurality of light-emitting diodes and the control unitis positioned in the opening; and a resin layer is formed on theinsulating layer.

According to the present invention, in a liquid crystal display deviceusing a light-emitting element as a light source, it is possible torealize a liquid crystal display device including a light source whichis easily treated and has high reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block view showing the configuration of a liquidcrystal display device according to an embodiment of the presentinvention.

FIG. 2 is a schematic diagram showing a light-emitting diode of theliquid crystal display device according to the embodiment of the presentinvention.

FIG. 3 is a schematic diagram showing a state that a light-emittingdiode of the liquid crystal display device according to the embodimentof the present invention is mounted on a metal substrate.

FIG. 4 is a schematic diagram showing a plate-shaped light source of aliquid crystal display device according to an embodiment of the presentinvention.

FIG. 5 is a schematic diagram showing a plate-shaped light source of aliquid crystal display device according to an embodiment of the presentinvention.

FIG. 6 is a schematic diagram showing a plate-shaped light source of aliquid crystal display device according to an embodiment of the presentinvention.

FIG. 7 is a schematic diagram showing a plate-shaped light source of aliquid crystal display device according to an embodiment of the presentinvention.

FIG. 8 is a schematic cross-sectional view showing a state that thelight-emitting diode of the liquid crystal display device according tothe embodiment of the present invention is mounted on a metal substrate.

FIG. 9 is a schematic development view showing a backlight of a liquidcrystal display device according to an embodiment of the presentinvention.

FIG. 10 is a schematic view showing a backlight of a liquid crystaldisplay device according to an embodiment of the present invention.

FIG. 11 is a schematic view showing a backlight of a liquid crystaldisplay device according to an embodiment of the present invention.

FIG. 12 is a schematic view showing a backlight of a liquid crystaldisplay device according to an embodiment of the present invention.

FIG. 13 is a schematic development view showing a state that a liquidcrystal panel is mounted in a backlight of a liquid crystal displaydevice according to an embodiment of the present invention.

FIG. 14 is a schematic view showing a state that a liquid crystal panelis mounted in a backlight of a liquid crystal display device accordingto an embodiment of the present invention.

FIG. 15 is a schematic development view showing a planar light source ofa liquid crystal display device according to an embodiment of thepresent invention.

DESCRIPTION OF REFERENCE NUMERALS

1: liquid crystal display panel, 2: TFT substrate, 5: driving circuit,6: driving circuit, 8: pixel unit, 9: display region, 10: switchingelement, 12: pixel electrode, 13: storage capacitor, 21: gate line(scanning signal line), 22: image signal line, 70: FPC, 71:interconnection, 75: terminal, 80: control circuit, 110: backlight, 120:light guiding plate, 121: optical sheet, 130: plate-shaped light source,150: LED, 151: LED chip, 152: wire, 153: chip terminal, 154: chipmounting part, 155: cone-shaped reflection surface, 156: fluorescencelight-emitting unit, 157: chip substrate, 158: p electrode, 159: nelectrode, 160: mounting substrate, 161: metal substrate, 162:insulating layer, 163: interconnection, 164: surface insulating layer,165: pad, 166: mark, 167: mark, 168: external terminal, 169: sidesurface, 171: external connection terminal, 172: connector, 173:external connection wiring, 174: reflection resin material, 175: resinmaterial, 176: notch, 177: rear surface FPC, 178: light shieldingmember, 179: heat conduction member, 180: backlight, 181: upperreceiving case, 182: lower receiving case, 183: window, 184: concavepart, 185: convex part, 186: case notch, 187: plate-shaped light sourceholding part, 188: pressing member, 189: gap

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the attached drawings.

First Embodiment

FIG. 1 is a plan view showing the whole configuration of a liquidcrystal display device according to an embodiment of the presentinvention. In FIG. 1, the liquid crystal display device 100 includes aliquid crystal display panel 1, a backlight 110 and a control circuit80. The liquid crystal display panel 1 is formed by sealing a liquidcrystal layer between glass substrates having electrodes for formingpixels. A signal and power supply voltage, which are necessary for thedisplay of the liquid crystal display panel 1, are supplied from thecontrol circuit 80 to the liquid crystal display panel 1. The controlcircuit 80 is mounted on a flexible substrate 70, and a control signalis supplied to the liquid crystal display panel 1 throughinterconnections 71 and terminals 75.

The backlight 110 includes a light guide plate 120, a light source 130and a receiving case 180. The backlight 110 is provided for the purposeof irradiating light to the liquid crystal display panel 1. In theliquid crystal display panel 1, the transmission amount or reflectionamount of the light irradiated from the backlight 110 is controlled toperform the display. The backlight 110 overlaps the rear surface or thefront surface of the liquid crystal display panel 1 with respect to aviewer. In FIG. 1, for facilitation of understanding, the backlight isshown parallel to the liquid crystal display panel 1. The detailedconfiguration of the backlight 110 will be described later.

Pixel electrodes 12 are provided in pixel units 8 of the liquid crystaldisplay panel 1. A plurality of pixel units 8 are included in the liquidcrystal display panel 1 in a matrix. However, to avoid the complexity ofthe drawing, only one pixel unit 8 is shown in FIG. 1. The pixel units 8provided in the matrix form the display region 9, and each of the pixelunits 8 functions as a pixel of a display image to display an image inthe display region 9.

In FIG. 1, gate signal lines (also referred to as scanning signal lines)extending in an X direction are provided orthogonal to a Y direction,drain signal lines (also referred to as image signal lines) extending inthe Y direction are provided orthogonal to the X direction, and each ofthe pixel units 8 is formed in a region surrounded by the gate signallines 21 and the drain signal lines 22.

A switching element 10 is provided in the pixel unit 8. The gate signalline 21 supplies the control signal to turn on/off the switchingelements 10. An image signal transmitted through the drain signal lines22 is supplied to the pixel electrodes 12 by turning on the switchingelement 10.

The drain signal lines 22 are connected to a driving circuit 5 and thedriving circuit 5 outputs the image signal. The gate signal lines 21 areconnected to a driving circuit 6 and the driving circuit 6 outputs thecontrol signal. The gate signal lines 21, the drain signal lines 22, thedriving circuit 5 and the driving circuit 6 are formed on a TFTsubstrate 2.

Next, FIG. 2 shows a schematic configuration of an LED 150 which is alight-emitting device, wherein FIG. 2A is a cross-sectional viewthereof, FIG. 2B is a plan view thereof when viewed from alight-emitting surface side, and FIG. 2C is a plan view thereof whenviewed from a rear surface side. The LED 150 has a structure in which aLED chip 151 serving as a light-emitting unit is mounted on a chipsubstrate 157. The LED chip 151 has a pn junction and emits light havinga specific wavelength when a voltage is applied to the pn junction. A pelectrode (anode) 158 is provided in a p-type semiconductor layer and ann electrode (cathode) 159 is provided in an n-type semiconductor layer.

Wires 152 are connected to the p electrode 158 and the n electrode 159,respectively. The wires 152 electrically connect the chip terminal 153for connecting the LED 150 to an external terminal, and the P electrode158 and n electrode 159, respectively.

At the light-emitting surface side of the LED chip 151, a fluorescencelight-emitting unit 156 may be provided. The fluorescence light-emittingunit 156 has a function for converting the wavelength of the lightemitted from the LED chip 151. In addition, a reference numeral 155denotes a cone-shaped reflection surface which reflects light whichtravels in a horizontal direction to the emitting surface side. Areference numeral 166 denotes a mark for displaying the position of thecathode (or the anode).

The chip terminal 153 is connected to an external interconnection andthe like on the rear surface of the chip substrate 157 and extends fromthe rear surface of the chip substrate 157 through the side surfacethereof to the emitting surface side to form a chip mounting part 154.When the chip terminal 153 and the chip mounting part 154 are formed ofmetal having high light reflectivity, the chip mounting part 154 can beused as a light reflection surface. When the chip terminal 153 and thechip mounting part 154 are formed of metal having high heat conductivity(conductive member), the heat generated at the LED chip 151 can beradiated to the rear surface side of the chip substrate 157.

Next, a substrate on which the LED chip 151 is mounted will be describedwith reference to FIG. 3. FIG. 3A is a schematic cross-sectional viewshowing a state that the LED chip 151 is mounted on a metal substrate161 and FIG. 3B is a schematic front view of a portion in which the LEDchip 151 is mounted. In FIG. 3, a mounting substrate 160 is formed bycoating the metal substrate 161 with an insulating layer 162, and aninterconnection 163 formed of a conductive layer such as a copper foilis formed on the insulating layer 162. It is possible to efficientlyradiate the heat transmitted to the rear surface side of the chipsubstrate 157 by forming the mounting substrate 160 using metal. Inorder to improve the heat radiation, it is preferable that theinsulating layer 162 is thin such that a problem such as a short circuitor leakage does not occur. In the present invention, the thickness ofthe insulating layer 162 is about 0.12 mm and the heat conductivitythereof is about 6.5 W/m·K.

A pad 165 for connection is formed on the end of the interconnection andelectrically connected to the chip terminal 153 of the LED chip 151. Thesurface of the mounting substrate 160 is coated with a surfaceinsulating layer 164 and the interconnection is prevented from beingshort-circuited with other components on the surface of the mountingsubstrate 160 to maintain insulation with the pad 165. On the surface ofthe pad 165, the surface insulating layer 164 is removed in order to theelectrical connection with the chip terminal 153. A soldering paste isprinted on the portion of the pad 165 from which the surface insulatinglayer 164 is removed and the LED chip 151 is mounted on the mountingsubstrate 160 by a reflow process.

Since the soldering reflow process is used, a material having a lowaffinity with a solder is selected as the surface insulating layer 164.Since the surface insulating layer 164 is formed on the surface of themounting substrate 160, the surface insulating layer 164 preferably hasan achromatic color. In particular, in consideration of light useefficiency, the surface insulating layer 164 preferably has a whitecolor or a color close to a white color for reflecting a large amount oflight. For a material having high reflectivity, titanium oxide issuitable. A reference numeral 167 is a mark indicating the position of acathode (or an anode). In order to improve visibility, a color differentfrom the color used in the surface insulating layer 164 is used.

FIG. 4 is a schematic diagram showing a state that the LED 150 islinearly mounted on the mounting substrate 160, wherein FIG. 4A is aplan view thereof, FIG. 4B is a cross-sectional view thereof, and FIG.4C is a perspective view showing a state that external connectionwirings 173 are connected.

In FIG. 4, six LEDs 150 are arranged on the mounting substrate 160 so asto configure a linear light source. In the LED chip 151, a constantvoltage difference occurs at the pn junction due to the diodecharacteristics. The voltage difference at the pn junction variesdepending on the manufacturing process. Accordingly, an optimal voltageis controlled to be applied to the pn junction. However, when an nnumber of LED chips 151 are connected in parallel, an n number ofcontrol circuits are required and thus manufacturing cost for thecontrol increases.

In FIG. 4, the LEDs 150 are connected in series three by three and avoltage is controlled in three LEDs. When a power supply voltage is 12V,which is used in a vehicle, and a potential difference which occurs inthe LED chip 151 is about 4V, it is efficient that three LEDs areconnected in series. That is, the connection is efficient when therelationship of V>n×Vd is established, where a power supply voltage isV, the potential difference is Vd which occurs in the LED chip 151, andthe number is n.

When a potential difference which occurs in each LED chip 151 is about3V and a power supply voltage is 12V, it is efficient that four LEDs areconnected in series. When a resistor is inserted between a final LEDchip 151 of n LED chips 151 connected in series and ground to performthe control, two interconnections are required in the serial connection.In the present embodiment, four interconnections are used and anexternal connection terminal 171 is formed on each interconnection. Asshown in FIG. 4C, the external connection terminals 171 are connectedwith the external connection wirings 173. Connectors 172 are provided onthe ends of the external connection wirings 173 and connected to thecontrol circuit 80 shown in FIG. 1.

FIG. 5 is a perspective view showing the structure of the metalsubstrate 161 having a box shape, wherein FIG. 5A shows the structure inwhich frame-shaped side surfaces 169 are formed at the circumferences ofthe metal substrate 161. The side surfaces 169 are formed to surroundthe metal substrate 161 and form a container having an emitting port foremitting light from the LEDs 150 upward.

In FIG. 5B, the insulating layer 162, the interconnection 163 and thesurface insulating layer 164 shown in FIGS. 3 and 4C are formed and themounting substrate 160 in which the LEDs 150 are mounted is received inthe container of the metal substrate 161 having the box shape. Theexternal connections 173 are led out of the mounting substrate 160through the upper end of the side surface 169.

FIG. 5C shows the structure in which a resin material 175 is filled inthe container formed by the metal substrate 161. The resin material 175is filled to bury portions other than the upper surfaces of the LEDs150. As shown in FIG. 5C, when the metal substrate 161 has the box shapeand the resin material 175 is filled in the container, the mountingsubstrate 160 can be treated as one plate-shaped light source.Hereinafter, the structure in which the resin material 175 is filled(coated) in the mounting substrate 160 is also called a plate-shapedlight source unit 130.

When the resin material 175 having heat conductivity higher than that ofair is used, heat radiation effect is improved. While the heatconductivity of air is about 0.0261 W/m·K, the heat conductivity ofepoxy resin is about 0.3 W/m·K, the heat conductivity of acrylic resinis about 0.21 W/m·K, and the heat conductivity of polycarbonate resin isabout 0.23 W/m·K as the reference of the heat conductivity of resin,which is improved by about one digit compared with air.

The external connection wirings 173 are fixed with the resin material175 to be easily treated and are externally led out through the upperend of the side surface 169. Accordingly, a problem occurs in that thethickness of the plate-shaped light source 130 increases by thethickness of the external connection wiring 173. A problem also occursin that a gap between the light-emitting surface of the plate-shapedlight source 130 and the light guide plate 120 is generated by theexternal connection wirings 173.

Next, the structure in which the resin material 175 is filled in theplate-shaped light source 130 will be described with reference to FIG.6. FIG. 6A is a plan view when viewed from the upper side of theplate-shaped light source 130. The resin material 175 is filled in thecontainer surrounded by the side surfaces 169. The resin material 175covers other portions than the upper surfaces of the LEDs 150. FIG. 6Bis a cross-sectional view showing the plate-shaped light source 130. Theresin material 175 is filled between the LEDs 150 to expose the uppersurfaces of the LEDs 150 and has a thickness substantially equal to thethickness of the LEDs 150.

When the height of the upper ends of the side surfaces 169 is equal tothat of the upper surfaces of the LEDs 150, the light-emitting surfaceincluding the plane of the resin material 175 is planarized. The upperend of the side surface 169 may contact the light guiding plate 120 byincreasing the height of the side surface 169 to some extent such thatan air layer is formed between the light guiding plate 120 and the uppersurfaces of the LEDs 150.

In FIG. 6C, the frame-shaped side surfaces 169 surround thecircumference of the metal substrate 161. A process of forming the metalsubstrate 161 in a planar state into the box shape may be omitted. InFIG. 6D, the frame-shaped side surfaces are removed after filling theresin material 175. Accordingly, the process is simplified and theexternal connection wirings 173 are easily led out. When light leaksfrom the side surfaces, a process of coating the side surface may beperformed such that a light shielding portion is formed at the sidesurface.

FIG. 7 is a view showing a structure formed such that the externalconnection wirings 173 are led out. As shown in the plan view of FIG.7A, notches 176 are formed in the longitudinal end surface of the sidesurface 169 such that the external connection wirings 173 are insertedinto the notches 176 to be led out to the external of the plate-shapedlight source 130.

As shown in the perspective view of FIG. 7B, the notches 176 areprovided on extension lines of the external terminals 171 and have awidth nearly equal to the diameter of the external connection wirings173. Since the notches 176 have the width nearly equal to the diameterof the external connection wirings 173, it is possible to prevent theresin material 175 from flowing out through the gaps of the notches 176.

As shown in the perspective view of FIG. 7C, when the externalconnection wirings 173 are led out through the notches 176 of the sidesurface 169, the increase of the thickness of the plate-shaped lightsource 130 is suppressed while the external connection wirings 173 donot overlap the upper end of the side surface 169. When light leaks fromthe notches 176, a light shielding member may be formed on the resinmaterial 175 close to the notches 176 or coloring to the resin material175 may be performed.

FIG. 8A is a cross-sectional view showing main parts in order to explainthe structure in which a reflection layer 174 is formed on the uppersurface of the resin material 175. When the plate-shaped light source130 is provided in the vicinity of the light guiding plate 120, thelight reflected from the light guiding plate 120 is reflected from thereflection layer 174 and emitted toward the light guiding plate 120. Thereflection layer 174 preferably has an achromatic color, but may becolored if brightness is corrected with respect to a specific color. Itis possible to improve heat radiation effect by forming the reflectionlayer 174 using a material having a high reflectivity and high heatconductivity, such as titanium oxide.

FIG. 8B is a cross-sectional view showing main part in order to explainthe structure in which the cone-shaped reflection surface 155 is removedand a member for scattering light is mixed in the resin material 175.Among the light emitted from the fluorescence light-emitting unit 156,the light incident to the resin material 175 is scattered and a portionthereof is emitted to the light guiding plate 120. As described above,the surface insulating layer 164 having high reflectivity is provided onthe upper surface of the metal substrate 161 and the light reflectedfrom the surface insulating layer 164 is emitted to the light guidingplate 120. The surface insulating layer 164 preferably has an achromaticcolor, but may be colored if brightness is corrected with respect to aspecific color.

FIG. 9 is a development view showing the structure of the backlight 110for receiving the plate-shaped light source 130 and the light guidingplate 120. The plate-shaped light source 130 and the light guiding plate120 are inserted and maintained by an upper receiving case 181 and alower receiving case 182. Concave parts 184 are provided in the sidesurfaces of the upper receiving case 181 and convex parts 185 areprovided on the side surfaces of the lower receiving case 182 such thatthe convex parts 185 are fitted into the concave parts 184. Accordingly,the upper receiving case 181 and the lower receiving case 182 are fixedsuch that the plate-shaped light source 130 and the light guiding plate120 are maintained therein.

A window 183 is formed in the upper receiving case 181 such that thelight emitted from the light guiding plate 120 is irradiated to theliquid crystal display panel. Notches 186 for passing the externalconnection wirings 173 are formed in the upper receiving case 181 andthe lower receiving case 182.

FIG. 10 is a view illustrating a positional relationship between theplate-shaped light source 130 and the light guiding plate 120 receivedin the lower receiving case 182 and FIG. 10 is a schematic plan viewshowing the plate-shaped light source 130 and the light guiding plate120 received in the lower receiving case 182. A pressing member 188 isprovided between the side surface of the lower receiving case 182 andthe plate-shaped light source 130, and the plate-shaped light source 130is held such that the light emitting surface contacts the side surfaceof the light guiding plate 120, in order to prevent light from leakingfrom the gap between the plate-shaped light source 130 and the lightguiding plate 120. A reference numeral 178 indicates, for example, alight shielding member formed of a colored tape. The light shieldingmember 178 is attached to prevent light from leaking between theplate-shaped light source 130 and the light guiding plate 120.

As shown in FIG. 10, the pressing member 188 is provided between theplate-shaped light source 130 and the lower receiving case 182, and theplate-shaped light source 130 is held such that the light emittingsurface contacts the side surface of the light guiding plate 120.However, a gap 189 is generated between the sidewall of the lowerreceiving case 182 and the plate-shaped light source 130 by the pressingmember 188. Air can be convected by the gap 189 and thus the heatradiation effect of the plate-shaped light source 130 is improved.

FIG. 11 is a plan view showing the structure in which the inner surfaceof the lower receiving case 182, the rear surface of the plate-shapedlight source 130 and the side surface of the light guiding plate 120contact with each other to be held. The inner side surfaces of the lowerreceiving case 182 defines the positions of the plate-shaped lightsource 130 and the light guiding plate 120. However, in the structureshown in FIG. 11, the heat radiation effect of the plate-shaped lightsource 130 deteriorates when the heat conductivity of the lowerreceiving case 182 is low. Accordingly, a heat conduction member 179having high heat conductivity is provided on the sidewall of the lowerreceiving case 182 which contacts the rear surface of the plate-shapedlight source 130.

FIG. 12 is a development view of the backlight 110 in order to explainthe structure in which the plate-shaped light source 130 and the lightguiding plate 120 contact the inner surface of the lower receiving case182. The heat conduction member 179 is also formed in the upperreceiving case 181 similar to the lower receiving case 182. In FIG. 12,a window is formed at the position of the heat conduction member 179 toimprove the heat radiation effect by air convention. Even when the heatconduction member 179 is provided at the position of the window, it ispossible to improve the heat radiation effect.

FIG. 13 is a development view of a liquid crystal display deviceaccording to the present invention, in which the liquid crystal displaypanel 1 is mounted on the backlight 110. The liquid crystal displaypanel 1 is mounted at the side of the window 183 for emitting the lightof the backlight 110. An optical sheet 121 is provided, if necessary,between the liquid crystal display panel 1 and the backlight 110. Thecontrol circuit 80 is connected to the liquid crystal display panel 1through the flexible substrate 70.

FIG. 14 is a schematic view showing the structure in which the liquidcrystal display panel 1 is mounted on the backlight 110, wherein FIG.14A is a cross-sectional view thereof and FIG. 14B is a side viewthereof. As shown in FIG. 14A, the light-emitting surface of theplate-shaped light source 130 and the light entrance surface of thelight guiding plate 120 closely adhere to each other. The flexiblesubstrate 70 is bent to extend to the rear surface of the backlight 110and the control circuit 80 is provided on the rear surface of thebacklight 110.

As shown in FIG. 14B, the notch 186 is provided in the side surface ofthe backlight 110 and the external connection wirings 173 are led outthrough the notch 186 to be connected to the control circuit 80. Thenotch 186 is positioned to be close to the control circuit 80.

FIG. 15 is a development view of a planar light source in which theplate-shaped light source 130 is formed into a planar shape. As shown inFIG. 15A, the plurality of LEDs 150 are arranged in a matrix toconfigure the planar light source. As shown in FIG. 15B, a flexiblesubstrate 177 is provided on the rear surface to supply a voltage to theLEDs 150. The flexible substrate 177 and the LEDs 150 are connectedthrough notches (openings) 176 provided in the rear surface of the metalsubstrate 161. A connector 172 is provided on the end of the flexiblesubstrate 177 to be connected to the control circuit 80 and the like.

1. A liquid crystal display device comprising: a liquid crystal displaypanel in which a liquid crystal layer is provided between a pair oftransparent substrates having electrodes for forming pixels therein; anda backlight which irradiates light to a rear surface of the liquidcrystal display penal, wherein the backlight has a plurality oflight-emitting elements, a circuit substrate on which the plurality oflight-emitting elements are arranged, and a metal case for receiving thecircuit substrate, and includes a light source which is integrallyformed by filling a resin material on the circuit substrate in the metalcase.
 2. A liquid crystal display device comprising: a liquid crystaldisplay panel in which a liquid crystal layer is provided between a pairof transparent substrates having electrodes for forming pixels therein;and a light source which irradiates light to a rear surface of theliquid crystal display penal, wherein the light source has a pluralityof light-emitting diodes arranged linearly, a circuit substrate forelectrically connecting the plurality of light-emitting diodes, and acase having side surfaces and a bottom surface for receiving the circuitsubstrate, and is integrally formed by filling a resin material betweenthe plurality of light-emitting diodes and the side surfaces in thecase.
 3. A liquid crystal display device comprising: a liquid crystaldisplay panel in which a liquid crystal layer is provided between a pairof transparent substrates having electrodes for forming pixels therein;a backlight which irradiates light to a rear surface of the liquidcrystal display penal; and a control unit which controls the liquidcrystal display panel, wherein the backlight has a light guiding plateand a plate-shaped light source formed along one side of the lightguiding plate; the plate-shaped light source has a light-emittingsurface, a bottom facing the light-emitting surface, and side surfacesformed on the circumference of the bottom; the bottom has a metalsurface, an insulating layer covering the metal surface, and aninterconnection provided on the insulating layer; a plurality oflight-emitting diodes are electrically connected to the interconnection;an opening are formed in the side surfaces or the bottom; a connectionwiring for electrically connecting the plurality of light-emittingdiodes and the control unit is positioned in the opening; and a resinlayer is formed on the insulating layer.
 4. The liquid crystal displaydevice according to claim 1, wherein the light-emitting elements arelight-emitting diodes.
 5. The liquid crystal display device according toclaim 4, wherein the plurality of light-emitting diodes are divided intoat least two groups and a voltage is applied to each group of thelight-emitting diodes.
 6. The liquid crystal display device according toclaim 2, wherein the plurality of light-emitting diodes are divided intoat least two groups and a voltage is applied to each group of thelight-emitting diodes.
 7. The liquid crystal display device according toclaim 3, wherein the plurality of light-emitting diodes are divided intoat least two groups and a voltage is applied to each group of thelight-emitting diodes.
 8. The liquid crystal display device according toclaim 3, wherein resin is filled in the bottom of the plate-shaped lightsource.